Through complex calculations, however, Oszwałdowski, utić and Petukhov show that the quantum dot's two mobile electrons will actually influence the manganese spins differently.
That's because while one mobile electron prefers to stay in the middle of the quantum dot, the other prefers to locate further toward the edges. As a result, manganese atoms in different parts of the quantum dot receive different messages about which way to align their spins.
In the "tug-of-war" that ensues, the mobile electron that interacts more intensely with the manganese atoms "wins," aligning more spins and causing the quantum dot, as a whole, to be magnetic. (For a visual representation of this tug-of-war, see Figure 1.)
This prediction, if proven, could "completely alter the basic notions that we have about magnetic interactions," utić says.
"When you have two mobile electrons with opposite spins, the assumption is that there is a nice balance of up and down spins, and therefore, there is no magnetic message, or nothing that could be sent to align nearby manganese spins," he says. "But what we are saying is that it is actually a tug of war. The building blocks of magnetism are still mysterious and hold many surprises."
Scientists including UB Professor Athos Petrou, UB College of Arts and Sciences Dean Bruce McCombe and UB Vice President for Research Alexander Cartwright have demonstrated experimentally that in a quantum dot with just one mobile electron, the mobile electron will act as a magnetic messenger, robustly aligning the spins of adjacent manganese atoms (http://www.buffalo.edu/news/pdf/June11/Paper2.pdf).
Now, Petrou and his collaborators are interested in taking their research a step further and testing the tug-of-war prediction for two-electron quantum dots, utić says.
utić adds that learning more about magnetism is important as soci
|Contact: Charlotte Hsu|
University at Buffalo